The liquid-liquid equilibrium (LLE) experimental data, including the binodal curve and the tie line of the aqueous two phase systems (ATPS) for two different molecular weights of ethylene oxide-propylene oxide copolymer (2500, 12000) and sodium citrate salt, are presented in two categories: first at different pH values 5, 7, and 8.2 at a constant temperature 25 degrees C and second at a constant pH of 8.2 with different temperatures of 25 degrees C, 30 degrees C, and 40 degrees C. It is found out that increases in the molecular weight of the polymer, pH, and temperature cause an increase of the two-phase region. Moreover, the experimental binodal data of the considered systems are successfully fitted to the Merchuk equation with significant R-2 and low standard deviation.